Concourse ATC checks for existence of resource-type-defaults.yuml

[jmatsushita]

Not sure when this was introduced, but I can't deploy the ATC with concourse version 6.7.4.

The web node fails on this task https://github.com/ahelal/ansible-concourse/blob/master/tasks/web_nix.yml#L74 with the error:

fatal: [10.8.2.61]: FAILED! => {"changed": false, "msg": "Unable to start service concourse-web: Job for concourse-web.service failed because the control process exited with error code.\nSee \"systemctl status concourse-web.service\" and \"journalctl -xe\" for details.\n"}

The journal shows:

error: invalid argument for flag `--base-resource-type-defaults' (expected flag.File): stat /mnt/concourse/resource-type-defaults.yml: no such file or directory

Submitting a fix now.